This was tricky to narrow down and make a repro and write a description but is seriously annoying thing for editing text for me on Chrome. I hope you guys would be able to look at it and write a better description.

Version: 51
OS: OS X 10.11.5

What steps will reproduce the problem?
1. Open
data:text/html;charset=utf8,<textarea style="font-size: 300%">asdasdasdasdasdasd
2. Select second and third character with double tap and select touchpad gesture but don't stop holding of touchpad tap
3. Press a key on your keyboard while not leaving tap gesture
4. Move touchpad cursor

What is the expected output?
After pressing a key on keyboard double tab and text highlight should be stopped, IMO

What do you see instead?
But with move of mouse cursor after inserting a letter, you see keyboard cursor is still moving around and that is making editing unpredictable. Even the fact this gesture is available on Windows and on other browsers as well, it seems on Mac this is more making issue at least for me as an user, I guess Mac sometimes don't understand touch tapping is stopped and I guess thats why I see the issue on it more.